Fuel pump for diesel engines



March 6, 1934. A. DUSSMANN FUEL PUMP FOR DIESEL ENGINES Filed March 13,1931 "Ann Il/I/I/I/ I .70 ran for.

Patented Mar. 6, 1934 UNITED STAT-ES FUEL PUMP FOR DIESEL ENGINES AugustDussmann, Aschaflenburg, Germany Application March 13,

1931, Serifl No. 522,458

In Germany July 16, 1930 2 Claims.

In the case of the Diesel engines with injected air, the atomization ofthe fuel and also the regulation of the quantity, especially in engineswith large variations of speed, can be obtained comparatively morereliably than in compressorless engines. However, the complicatedarrangements for producing the injection air require expensive plants.The Diesel engine with pressure injection is much more simple and justas reliable when the following conditions are fulfilled:

1. The control of the fuel pump must, if possible, act so that thecommencement of the injection always occurs at the same time, the, endof the injection occurring however, earlier or later according to theload. This problem is mostly solved by separately controlled closingelements, rotary valves or slides, which however results in complicatedconstructions with high back pressure on the regulator.

According to the invention, uniform commencement of the injection isobtained, with a simple regulation of the quantity of fuel, in thatthepump plunger is turned so that the pressure chamber is connectedsooner or later with the suction chamber of the pump by means of thebores provided in the plunger.

2. The spring-loaded shutting off element in front of the nozzle, sinceit wears out quickly, should if possible be avoided and replaced by asimple open nozzle. However, the fuel jet must then be forced throughthe nozzle at the greatest possible speed. This is effected according tothe invention in that the feed stroke of the pump does not begin at thecommencement of the cam incline but at the middle, when the pump plungerhas already attained a high spee 3. In the case of engines, especiallyvehicle engines, which are subject to great variations of speed andload, the speed of the pump plunger must always remain uniform.independently of the running speed of the engine, so that the atomizingoccurs in uniform quality also at low-. er speeds and when starting upthe engine. This condition is fulfilled according to the invention inthat the pump plunger is actuated not by a cam, the angular speed ofwhich is dependent on the running speed of the engine, but by means of amedium capable of expansion, for example an ignitable mixture orcompressed air.

Two embodiments of the fuel pump according to the invention for Dieselengines with pressure injection are illustrated by way of example in theaccompanying drawing in which:-

Fig. 1 shows in vertical section a pump equipped with valve control.

Fig. 2 is a similar view of a modified form of construction.

The constructions illustrated in the drawing are characterized chieflyby the fact that the feed stroke of the fuel pump piston is effectedjerklike by compressed air, which is sucked in and compressed by aseparately arranged compressor.

The crank shaft 22, which is driven by the englne, actuates thecompressor piston 24 through the connecting rod 23, which compressorreciprocates vertically, suction-tight, in the pump casing 25. In thelower dead centre position, the upper edge of the compressor piston 24intersects with the lower edge of the air suction slot 26. Thecompressor cylinder 27 is filled with atmospheric air. This iscompressed after the compressor piston 24 has passed the suction slot26. Shortly before reaching the upper dead centre position, thecompressor piston 24 pushes open the pressure valve 29 hitherto heldclosed by the spring 28. The compressed air flows into the cylinder 30.A piston 31 moves in the cylinder 30. The force of the spring 28 isselected so that it separates the cylinder 27 from thecylinder 30 withthe surface of the pressure valve 29 against the maximum pressure of thecompressed air. If the valve 29 is pushed up by the piston 24, thecompressed air acts on the considerably larger surface of the piston 31.Consequently this piston is driven upwards with a jerk like movement.The speed of the piston 31 depends chiefly upon the air pressure and onthe counter pressure in the pump cylinder, which depends chiefly uponthe crosssection of the nozzle. Consequently, the speed of the piston 31is always uniform under the same conditions independently of the numberof revolutions of the engine.

During the outward movement of the compressor piston 24, the compressedair in the cylinder 30 returns through the suction valve 32 into thepump cylinder 27, a portion of the work expended for the compressionbeing recuperated. The air losses due to leakages may be made goodthrough air sucked in through the suction slot 26 in the lower deadcentre position. The spring 28 forces the piston 31 back on to thepressure valve 29, and the suction valve 32 also closes, when thecompressor piston 24 has passed the suction slot 26 on the inwardmovement.

The fuel pump plunger 6 is mounted on the piston 31 and is moved duringthe suction stroke by the washer 7 in a similar manner to that in thecam pump. The regulation of the quantity of fuel is also effected byturning the pump plunger 6, whereby the pump pressure chamber isconnected earlier or later with the suction chamber.

In the case of pumps for small engines the valve control of thecompressed air presents a complication which could cause trouble owingto the delicacy of the valve packings.

Fig. 2 shows the pump with simple slot control, with which exactly thesame effect is obtained as with the pump illustrated in Fig. 1.

The piston 33 is also actuated by a crank drive. In the lower deadcentre, atmospheric air enters through the suction slot 34 into thecompressor cylinder 35. The running surface has an overflow slot 36,which connects the compressor cylinder 35 to the cylinder 37. The piston33 has a U-shaped cross section 38. A piston cavity is thereby formed,in which a cylinder cover 39 fits. The piston 33 has a slot 40 whichregisters with the suction slot 34 in the lower dead centre and with theoverflow slot 36 in the upper dead centre. The air sucked through thesuction slot 34 is therefore compressed, and only on attaining themaximum pressure suddenly flows through the overflow slot 36 into thecylinder 37 in which the piston 41 moves.

The connection of the pump plunger 6 and the adjustment of the quantityof fuel are effected in the same manner as in the pump according to Fig.1.

I claim:-

1. A fuel pump for Diesel engines with pressure injection with an aircompressor for producing compressed air for actuating the pump,comprising in combination with the compressor cylinder, a compressorpiston adapted to suck in and compress air, a valve adapted to open andallow the passage of the compressed air towards the end of thecompressing stroke at the highest air pressure, a further cylinderspacially separated from said compressor cylinder adapted to suddenlyreceive the compressed air through said valve, a piston in said separatecylinder adapted to be moved ata high speed by the air suddenly enteringsaid separate cylinder, an injection pump fixed on said last mentionedpiston, and a nozzle adapted to inject the sucked in fuel underpressure.

2. A fuel pump for Diesel engines with pressure injection, comprising incombination with the pump piston, a compressor adapted to supply air fordriving the fuel pump, a piston for said compressor of U-shaped sectionhaving a slot leading from the cavity to the running surface of saidpiston compressor, a cylinder cover adapted to project into the cavityformed in said piston, a wall of said compressor cylinder having asuction and an overflow slot, and a compartment communicating with saidcylinder through said overflow slot, the slots in said cylinder walladapted to be controlled by the slot in said piston, so that thecompressed air suddenly strikes against the pump piston only on themaximum pressure being reached.

AUGUST DUSSMANN.

